Activated sludge and clarifiers: wastewater treatment plants in Pennsylvania
234 plants · 30% of the state · 374 MGD reported by 231 plants
Klarifi identifies 234 publicly owned wastewater treatment plants with activated sludge and clarifiers in Pennsylvania, 30% of the 783 plants in the state (374 MGD reported by 231 plants). The largest is City Of Allentown Wastewater Treatment Plant in Allentown at 31.07 MGD.
Activated sludge is the standard mechanical process for cities: aeration basins where bacteria consume organic matter, followed by clarifiers that settle the biomass out. These plants are identified by their circular or rectangular clarifiers and by the suspended-growth process code, and they are the main market for blowers, diffusers, clarifier mechanisms and instrumentation.
The largest activated sludge plants in Pennsylvania
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | City Of Allentown Wastewater Treatment Plant | Allentown | 31.07 | PA0026000 | Sep 2007 | 0 |
| 2 | Delcora-Western Regional Treatment Plant | Chester | 27.54 | PA0027103 | Mar 2026 | 18 |
| 3 | City Of Erie, Pa - Wastewater Treatment Plant | Erie | 24.1 | PAL026301 | Dec 2030 | 1 |
| 4 | Wyoming Valley Sani Auth Wilkes Barre | Wilkes Barre | 17.3 | PAL026107 | Dec 2030 | 1 |
| 5 | Reading STP | Reading | 14.09 | PA0026549 | Apr 2028 | 9 |
| 6 | City Of Bethlehem Wastewater Treatment Plant | Bethlehem | 9.97 | PA0026042 | May 2031 | 18 |
| 7 | Springettsbury Wastewater Treatment Plant | York | 7.61 | PAL026808 | Dec 2030 | 4 |
| 8 | Lrbsa - Throop Plant | Throop | 5.7 | PA0027090 | Aug 2021 | 6 |
| 9 | Oaks WWTP (lower Perkiomen Valley) | Oaks | 5.54 | PA0026964 | Nov 2030 | 5 |
| 10 | Lower Bucks WWTP | Levittown | 5.34 | PA0026468 | May 2028 | 25 |
| 11 | Lebanon City STP | Lebanon | 5.22 | PAL027316 | Dec 2030 | 1 |
| 12 | Chambersburg Boro STP | Chambersburg | 5.16 | PAL026051 | Dec 2030 | 0 |
| 13 | Gr Hazleton Jt Sew Auth WWTP | Hazleton | 5.15 | PA0026921 | Feb 2027 | 6 |
| 14 | Valley Forge Sewer Authority WWTP | Phoenixville | 4.66 | PAL043974 | Dec 2030 | 8 |
| 15 | Washington E Washington STP | Washington | 4.51 | PA0026212 | Jan 2031 | 174 |
| 16 | Lower Allen Twp STP | New Cumberland | 4.33 | PAL027189 | Dec 2030 | 0 |
| 17 | Uniontown STP | Uniontown | 4.2 | PA0027219 | Jul 2027 | 6 |
| 18 | Norristown Muni STP | Norristown | 3.96 | PA0027421 | May 2029 | 2 |
| 19 | Log College STP | Warminster | 3.78 | PA0026166 | Aug 2026 | 7 |
| 20 | Hanover Boro STP | Mcsherrystown | 3.65 | PA0026875 | Dec 2027 | 2 |
| 21 | E Norriton Plymouth /norristown | Plymouth Meeting | 3.6 | PAL026816 | Dec 2030 | 7 |
| 22 | Indiana Boro WWTP | Indiana | 3.43 | PA0026751 | Jun 2031 | 0 |
| 23 | Pottstown Wastewater Treatment Plant | Pottstown | 3.34 | PAL026786 | Dec 2030 | 16 |
| 24 | Piney Fork STP | Pittsburgh | 3.22 | PA0027618 | Jun 2028 | 15 |
| 25 | Morrisville Borough STP | Morrisville | 3.21 | PA0026701 | Feb 2031 | 23 |
Contacts and project signals for every plant on this list
Klarifi adds verified decision-maker contacts, permit limits, discharge monitoring data and the capital projects planned in each city, filterable by technology, size and compliance record.
Other technologies in Pennsylvania
Activated sludge and clarifiers in other states
Activated sludge and clarifiers in Pennsylvania: questions
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
Data refreshed September 11, 2026.